#include<iostream>
#include<string>

class MyString:public std::string
{
public:
    MyString(const char*str):std::string(str){}//类的构造是特有的

private:
    std::string str;
};


int main ()
{
    //std::string s1 = "hello";
    MyString s = "hello";
    s+="world";
    std::cout<<s<<std::endl;
    return 0;
}